Introduction of four aryl groups on the highly reactive
o-quinodimethane (
o-QDM) skeleton suppresses the intermolecular reactivities. Thus, the unimolecular isomerization through electrocyclization is the major decomposition path for title molecules. Rational design can prevent thermal isomerization of Ar
4-
o-QDMs. A new general procedure to generate Ar
4-
o-QDM has been established here that includes two-electron reduction of the corresponding dications, whose reaction conditions no longer promote electrocyclization of Ar
4-
o-QDM. Several derivatives of Ar
4-
o-QDM with the dihydrophenanthrene, dibenzoperylene, or acenaphthene skeleton were isolated for the first time, and the details on their highly strained molecular structures were investigated by low-temperature X-ray analyses. Based on the reversible interconversion between Ar
4-
o-QDMs and the precursor dications, they represent a new class of electrochromic redox pairs.
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